Method of making screws



June 15, 1937. Y E. E. CLARK 2,084,078

METHOD OF MAKING SCREWS Filed Nov. 15, 1935 iiii7 a I T W mm 45.

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@54 war u zz mwqaml Patented June 15, 1931 2,084,078"

UNIT D STATES PATENT orrica sia'rnon' time scnaws Eulenc lacluk,

Provlde nccrll; L, assignor' to American Screw Companmlrovid a corporation of Rhode Inland Application November 15, 1935, Serial No. ,042

6 Claim!- This invention relates to screws and themethods of making the same.

More particularly the'invention relates to screw heads and the methods of forming them including particularly the forming of a recess in the a screw of the t d typ 5 head for the accommodation of a screw driver. Figure 6 ws an operation similar to Figure 5 An important feature of the invention consists being performed on a round h d crew. in the provision of a screw having recess of Figure '7 shows the result of the conventional generally cruciform plan in which the intersec- Shaving Operation when applied o a sed lo tions or junctions of the recess walls with the Screw head in which no rounding f the junc- 10 surface of the h d of th screw are the t tions of the recess wall surfaces and the flat head sharp. The method of so forming these intersulfate has n'p nd sections simultaneously with t punching of the Figure 8 illustrates the manner of shaving the recess is a further factor of the invention and under Surface n y f a screw head. 1 leads to'improved results and-a, superior t, With the increased mechanization of industry Among the important advantages of t there has been an active demand for a screw sharp junctions may be enumerated the followwhich can be driven by p w m hinery more m satisfactorily than the conventional screw with A, Round eel-hers i h prevent the forming a transverse kerf in the head. This kerf .does go of burrs in case of slippage of th screw driven not prevent lateral movement of the screw driver 3 A compressing and hardening f t mete} in the direction of the kerf length so that slippage resulting from the extra compression at thejuncmay Occur resulting n r u marring of the ti further preventing formation. surface into which the screw is being driven by c, h presenting fv e e edge to t the rapidly rotating tool. Furthermore, such a g5 shaving t used in in the head urf c s screw cannot'be satisfactorily held on the head to prevent th turning of i t the recess of the driver for insertion in diflicultly accessible from the action of the cutter. Pl es. v y

1), Th provision f a superior and immediately This demand has resulted in the production of ab h d finish as a result of t puhehmg screws having a recessed head, no portion of the operation 50 t t t screw can he used f rough recess extending to the edge of the head whereby 30 pflrposes wit t any mm operation on the lateral slippage of the tool .18 prevented. The head, most satisfactory of these screws are those hav- Another important feature of 4 the invention 1113 a recess 0f generally cruciform P tapering resides in the formation of a screw head with an Slightly in Width from top to bottom d having unfinished, hard, recessed, top surface and a fin- Walls Substantially Straightiehed under urfa whereby a screw suitable for In the manufacture of such screws it has hereh use i formed t t minimum f operatofore been customary to punch the recess as a dong, part of the head upsetting operation or just suboth and further features and objects of the sequent to the substantial finishing'upset and to 40 m tt 111 he more apparent t those shined then machine the head on both its underneath 40 in the art upon a consideration of the accomand upper The customary Shari/111g D- hg drawing and r n spe ification eration, as applied to screws of the kerfed head wherein are disclosed several exemplary embo'ditype Prior to the kelffing, W h is e rn d out by ments 1 the arti l add preeese advancing a tool substantially at r ght angles to In said drawing: the axis of the screw while rotating the same 45 Figure 1 is an elevtmn or a blank or cannot be satisfactorily applied to the recessed mono! rod from wmch/ the Screwqs f d; screws. This is because the cutter in removing me 2 Shows intermediate step in the the metal adJacent to the edges of the recess um I when and throws down burrs or small shavings mto the prune of man ac g so 8 recess where they stick either because of fitting resentsa partially finished head upset on the tightly into the wings of the recess or becauseblank; v they are not completely severed from the metal 3 shows a screw in which the head is I of the head and these. burrs formobstructions complete form d and he rece p h and to the entrance of the screw driver. It is difiicult and expensive to remove them. Even small 56 illustrates the punch being withdrawn;

Figure 4 is a plan view on an enlarged scale showing a screw head completed as to punching and forming; n Y I Figure 5 shows the step of shaving or finishing l ing operation the fillet forms burrs and threads of metalprevent proper and accurate cohesion between the screw driver point and the recess so'that there is a possibility of ppage. 5 In accordance with the present invention the operation which forms the recess inthe screw head, and which is hereinafter called "punching", simultaneously forms a non-sharp Junction between each surface of the recess and the surface of the head. This junction is formed conveniently by applying a fillet to the punch, at the Junction of the punch nub and the head shaping shoulder which serves to finally form the head of the screw. During the last part of the punchthe rounded edges at the periphery of the recess and provides an additional compressing and-working oi the metal thereat which has been shown to materially harden the same preventing subsequent burring by the action of the screw driver particularly in the case of a slippage. This is exceedingly important .-for such burrs sometimes are very sharp and where the screw heads are exposed, often catch clothing or other fabrics.

'35 By now having reference to'the drawings, the

product and the process of forming the same will be more fully appreciated. In Figure 1 there is shown at It a blank comprising a section of .cylindrical wire or rod of suitable metal from .30 which the screw is adapted to be formed. This rod is held in the conventional anvil (not shown) and one end is struck by a suitable tool to upset it to form a bulbous head II as shownin Figure 2. While still held in the same anvil this head is subject to a punching or piercing operation from-the punch if having the suitably formed nub I; thereon surrounded by a shoulder It. The nub I 3 forms the desired shape of recess in the screw head and the shoulder It gives a final 40 form to the screw head by shaping-it to the de-,

sired configuration, fiat. as shown in Figure 3 although screws of round, oval, filister and other shaped heads can be formed in a similar manner.

The operation just described may be termed a two-stroke operation for forming and recessing the screw headalthough under certain conditions and for certain sizes of screws a threestroke operation is preferred, the first stroke forming a less pronounced bulb than shown in Figure 2, the second substantially finishing the head as to shape, and the third punching it and completing the shaping.

Figure 4 shows in plan a screw head as formed 55 by one of the described processes and it will be noted that the junctionsof the flat surface ll of the head and the various surfaces II of the walls of the recess are not sharp. They may be suitably curved to any desired radius, may be 60 chamfered or otherwise configured so that they are other than sharp lines formed by the intersections of substantially flat surfaces. This shaping of these junctions is performed during the punching operation and substantially along II on the punch and results from what may be termed a fillet 28 at the junction of the punch hub and the shoulder. As previously mentioned, the action of this fillet is a working and compressing of the metal at thesurface junctions which not only hardens the desired rounded edges at the periphery it of the recess I1.

Because of this relieving of the periphery, no 75 fins are formed by the punching operation such 1 being hardened,

with the final shaping oi the head by the shoulder same but forms the as have been found to exist where this relieving does not take place. The screw is thus immediately ready for use for rough purposeswlthout any further treatment except the customary threading which is the same as on all prior art screws. The rounded periphery of the recess resists abrasion and burring by the action of the screw driver and ensures an easy entrance of the driver into the recess as well as provides asubstantiailyilat head without any protrudingslivers of metal.

This shaping of the periphery of the recess, however, has a further important advantage in the event that the screw head is to be-flnished by shaving. 'I'his shaving is a machine operation similar to turning wherein usually both the upper and lower surfaces of the head are shaped simultaneously by a single cutting tool prmented to the head along a line substantially at right angles to-the axis 01 the screw about which it is being rotated at the time of the cutting. This operation is shown in Figure 5 where the shank I ll of the screw is .considered as being held in a chuck and rotated and the tool It, having a surface lfl'for cutting the underside of the screw head, is being advanced at right angles to the axis of rotation of the screw shank. The other cutting edge 20 of the tool is substantially parallel to the line of movement of the tool. The whole assembly is so adjusted that the edge Ill cuts through the curved junction it previously described substantially tangentially to the curve so that there is no tendency to throw in burrs or shavings only partially severed from the head and thereby clog the narrow wing passages in the recess.

Figure 7 shows the results 01' cutting with the customary shaving tool where the screw head is not formed with the rounded edges at the periplicry of the recess and the turned-in burrs II can readily be seen.

Where screws have been made without the rounded surface at the periphery of the recess it has been customary in some cases to carry out the shaving-operation with a shortened edge III on the tool which does not reach to the recess and to then finish. off the remainder of the head around the recess with an end mill, but this is an additional operation and an added expense in the manufacture which is not justified in the product. In accordance with the present invention equally as fine a screw head is effected with.- out anyv burrs and without the additional operation. v

In Figure 6 a screw having a so-called round head 22 is shown but here the shaving takes place the same as in Figure 5 with the tool 28 having a straight cutting-edge 24 for the fiat under-surface of the screw head and an arcuate edge 25 for the curved upper portion of the head. In order that the cutting of this edge 25 may be substantially tangential to the curved surface at the junction of the screw head and recess walls, this curved surfacemay have to be more pronounced because of the curvature of the head. but its efi'ect is as good with the fiat headed screw and the articles are turned out rapidly and without the need of a further operation to clear the recess.

Where the heads of screws do not show in unished work the upper surface need not be finished more than the rough shaping resulting from the upsetting as previously described. This leaves a hard surface which is very desirable. It is sometimes desirable to finish the undersurface Cal - within an enlarged head, forming junctions beof the head in order to give a firm. accurate seating against the material into or through which the screw is inserted although a, fair finish-results" from the anvil surface used during the upsetting.

Figure 8 shows the manner of machining or shaving only the undersurface, for instance, of a so-called oval headed screw. The tool has a lip which is unsharpened and acts only as a gauge in common with the shoulder 29 to provide accurate means for sizing the head while the cutting edge 21 acts alone to remove metal from only the underside ofthe head as shown.

It will be understood that the superior quality of the product is due to the rounded edges of the recess periphery and to the hardening of the same, all of which results from the novel proces of forming the recess.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. The method of making screws comprising upsetting a head on a suitable rod, forcing a punch into the head to form a recess therein, forming an arcuate junction between the walls of the recess and the upper surface of the head and simultaneously shaving the upper and lower surfaces of the head to finish the same.

I 2. The method of making screws comprising heading and punching a recess in a suitable rod,

forming a curved junction between the walls of the recess and the upper surface of the head and then shaving the upper surface of the head substantially tangential to the curve of said junction.

3'. The method of forming a screw from a wire orrod comprising forcing a punch into the end of the rod to form a screw driver receiving recess I tween all surfaces of the recess and the upper surface of the head which are other than sharp intersections, and then shaving the surface of the head with a stationary cutting tool while rotatingthe rod about its axis.

'4. The method of forming a screw from a rod comprising piercing and upsetting the rod axially to form a head and screw driver receiving recess of substantially cruciform plan, forming during the punching operation junctions between the surfaces of the recess and the surface of the head which are relieved, and then finishing the said surface of the head bya single machining operation without entirely removing the said relieved junctions.

5. The method of forming a screw from a rod comprising simultaneously piercing and upsetting an end of the rod axially to form a head with a screw driver recess therein of substantially cruciform plan with substantially flat walls, forming during the punching operation a gradual merging of the surfaces of the recess and of the head,"rotating the rod about its axis and finishing the head by advancing a cutter at right angles to said axis into such a position as to cut through said merging portions but notthrough the flat'wails of the recess.

6. The method of forming a screw from a rod comprising upsetting and piercing the rod axially to form a head with a screw driver recess therein of substantially cruciform plan with substantially flat walls, finishing the pierced head surface by a simple turning operation, one of the steps prior to the finishing providing such a junction between the head surface and the recess surfaces that it prevents burrs or chips being turned into the recess dining the finishing operation.

EUGENEE. cm i 

